1. Field
The invention is in the field of archery bows of the type wherein the force required to draw the bow is greater than the force required to hold the bow in its drawn position.
2. State of the Art
Most archery bows include a handle or riser section with a pair of elongate limbs fixed thereto and extending from opposite ends thereof. A bowstring is coupled to the free ends of the limbs so that upon drawing the bowstring, the limbs are deformed, thereby storing energy in the limbs. Upon release of the bowstring, the deformed limbs forcefully return to their rest positions, releasing the stored energy to the bowstring and an arrow nocked thereon. Such bows are normally designed to have a certain draw length and draw weight. With traditional compound archery bows, eccentrics are rotatably mounted on the outer ends of the upper and lower limbs, respectfully. The eccentrics determine the characteristics of the force-draw curve of the bow and provide a let-off, i.e., a reduction of the force required to hold the bow in drawn position as opposed to the force required to draw the bow through intermediate positions of the draw. The let off provided for a particular compound bow is normally designed into the bow and is related to the draw weight and draw length. Adjustment of the draw weight and draw length of the bow can usually be made within certain ranges by changing the length of the bowstring, the attachment of the limbs to the handle, the length of the buss cables, and/or the size or configuration of the eccentrics. Usually, such adjustment is difficult for the archer to perform himself and the range of adjustment is limited. In addition, all adjustments are interrelated so that, for example, an adjustment of the bow limbs to increase the draw weight, also changes the draw length. Further, the efficiency of traditional compound bows which provide relatively substantial limb tip travel to move the bow string from drawn to rest position is limited by the mass of such limb tips and associated eccentrics which must accelerate and move from the drawn to rest positions.
Various attempts have been made to increase the efficiency of a bow and to make adjustment of the draw length, draw weight, and let off easy for the archer and relatively independent of one another. These attempts have generally included pivoting the limbs of the bow to the riser section, making the limbs very stiff to minimize deformation, and providing some type of energy storage means, such as a spring, coupled to the bow limbs to store energy as the bow limbs pivot about their mounting to the riser as the bow is drawn. However, such bows have not been entirely satisfactory and have not gained acceptance and wide use. Room remains for a bow with increased efficiency and increased ease of adjustment of the draw length, draw weight, and let off.